Speed is not the issue. Volume and pressure is. Typically, you want to spend 10-15 hp to make several psi for a small engine, and something like 25 hp for a bigger one.
Thomas Knight's E-Charger has a 15 hp triple electric motor.
One car magazine took two huge leaf blowers and mated them to a Vette and got around 6 psi, if I recall... on a big arse V8.
EDIT: found it. Fascinating read:
http://www.hotrod.com/techarticles/e...r/viewall.html
(two 470 CFM blowers. 25 hp gain... okay, I was wrong... it was ONE psi.
)
150 cfm could probably net you 1 psi of boost on a small four-banger. At just above idle.
Won't do much else. Maybe six of those would be enough to not be an intake restriction.